diff --git a/.github/workflows/make-test.yml b/.github/workflows/make-test.yml
index c1fa406f990..7034e394090 100644
--- a/.github/workflows/make-test.yml
+++ b/.github/workflows/make-test.yml
@@ -109,3 +109,28 @@ jobs:
        su -c ldconfig
     - name: Test Python3
       run: python3 -c "import gnuradio.blocks; print(gnuradio.blocks.complex_to_float())"
+  no-python:
+  # All of these shall depend on the formatting check (needs: check-formatting)
+    needs: [check-formatting, check-python-formatting]
+    runs-on: ubuntu-latest
+    # The GH default is 360 minutes (it's also the max as of Feb-2021). However
+    # we should fail sooner. The only reason to exceed this time is if a test
+    # hangs.
+    timeout-minutes: 120
+    name: C++ Only Build (Ubuntu 20.04)
+    container:
+      image: 'gnuradio/ci:ubuntu-20.04-3.9'
+      volumes:
+        - build_data:/build
+      options: --cpus 2
+    steps:
+    - uses: actions/checkout@v2
+      name: Checkout Project
+    - name: CMake
+      env:
+        CXXFLAGS: -Werror -Wno-error=invalid-pch
+      run: 'cd /build && cmake ${GITHUB_WORKSPACE} -DENABLE_DOXYGEN=OFF -DENABLE_PYTHON=OFF'
+    - name: Make
+      run: 'cd /build && make -j2 -k'
+    - name: Make Test
+      run: 'cd /build && ctest --output-on-failure'
diff --git a/CMakeLists.txt b/CMakeLists.txt
index bd53d0edf29..26a99c4ee50 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -264,9 +264,12 @@ if(NOT PYGCCXML_FOUND)
     message(STATUS "******************************************************************")
 endif()
 
-find_package(pybind11 REQUIRED)
+find_package(pybind11)
+IF(pybind11_FOUND)
 IF(${pybind11_VERSION} VERSION_LESS ${PYBIND11_MIN_VERSION})
-    message(FATAL_ERROR "pybind11 version ${pybind11_VERSION} < ${PYBIND11_MIN_VERSION}")
+    message(WARNING "pybind11 version ${pybind11_VERSION} < ${PYBIND11_MIN_VERSION}")
+    set(pybind11_FOUND False)
+ENDIF()
 ENDIF()
 
 include(GrComponent)
@@ -372,7 +375,6 @@ GR_REGISTER_COMPONENT("post-install" ENABLE_POSTINSTALL)
 ########################################################################
 add_subdirectory(docs)
 add_subdirectory(gnuradio-runtime)
-add_subdirectory(grc)
 add_subdirectory(gr-blocks)
 add_subdirectory(gr-fec)
 add_subdirectory(gr-fft)
@@ -387,13 +389,16 @@ add_subdirectory(gr-iio)
 add_subdirectory(gr-qtgui)
 add_subdirectory(gr-trellis)
 add_subdirectory(gr-uhd)
-add_subdirectory(gr-utils)
 add_subdirectory(gr-video-sdl)
 add_subdirectory(gr-vocoder)
 add_subdirectory(gr-wavelet)
 add_subdirectory(gr-zeromq)
 add_subdirectory(gr-network)
 add_subdirectory(gr-soapy)
+if (ENABLE_PYTHON)
+add_subdirectory(grc)
+add_subdirectory(gr-utils)
+endif()
 
 # Defining GR_CTRLPORT for gnuradio/config.h
 if(ENABLE_GR_CTRLPORT)
diff --git a/gnuradio-runtime/CMakeLists.txt b/gnuradio-runtime/CMakeLists.txt
index a81a5c14272..5160e76d8cd 100644
--- a/gnuradio-runtime/CMakeLists.txt
+++ b/gnuradio-runtime/CMakeLists.txt
@@ -28,6 +28,7 @@ find_package(spdlog CONFIG)
 # Register component
 ########################################################################
 include(GrComponent)
+if (ENABLE_PYTHON)
 GR_REGISTER_COMPONENT("gnuradio-runtime" ENABLE_GNURADIO_RUNTIME
     Boost_FOUND
     PYTHONINTERP_FOUND
@@ -35,6 +36,14 @@ GR_REGISTER_COMPONENT("gnuradio-runtime" ENABLE_GNURADIO_RUNTIME
     spdlog_FOUND
     pybind11_FOUND
 )
+else()
+GR_REGISTER_COMPONENT("gnuradio-runtime" ENABLE_GNURADIO_RUNTIME
+    Boost_FOUND
+    PYTHONINTERP_FOUND
+    MPLIB_FOUND
+    spdlog_FOUND
+)
+endif()
 
 get_filename_component(GNURADIO_RUNTIME_PYTHONPATH
     ${CMAKE_SOURCE_DIR}/python ABSOLUTE
diff --git a/gnuradio-runtime/lib/CMakeLists.txt b/gnuradio-runtime/lib/CMakeLists.txt
index 2d8a81ab10b..6cd9c0c54f9 100644
--- a/gnuradio-runtime/lib/CMakeLists.txt
+++ b/gnuradio-runtime/lib/CMakeLists.txt
@@ -52,7 +52,6 @@ add_library(gnuradio-runtime
   block.cc
   block_detail.cc
   block_executor.cc
-  block_gateway_impl.cc
   block_registry.cc
   buffer.cc
   buffer_double_mapped.cc
@@ -99,6 +98,12 @@ add_library(gnuradio-runtime
   vmcircbuf_sysv_shm.cc
   )
 
+if (ENABLE_PYTHON)
+  target_sources(gnuradio-runtime PRIVATE
+    block_gateway_impl.cc
+  )
+endif()
+
 # Messages
 target_sources(gnuradio-runtime PRIVATE
   ${CMAKE_CURRENT_SOURCE_DIR}/messages/msg_accepter.cc
@@ -135,14 +140,20 @@ target_link_libraries(gnuradio-runtime PUBLIC
   # INTERFACE/PRIVATE split so users of the library can choose how to link to Python
   # (importantly, extension modules can avoid linking against Python and resolve
   #  their own Python symbols at runtime through the Python interpreter's linking)
-  INTERFACE
-    Python::Module
   PRIVATE
-    Python::Python
-    libunwind::libunwind
-    pybind11::pybind11
+    libunwind::libunwind 
   )
 
+if (ENABLE_PYTHON)
+target_link_libraries(gnuradio-runtime
+  INTERFACE
+  Python::Module
+  PRIVATE
+  Python::Python
+  pybind11::pybind11
+)
+endif()
+
 # Address linker issues with std::filesystem on Centos 8 and Debian
 target_link_libraries(gnuradio-runtime PUBLIC $<$<AND:$<CXX_COMPILER_ID:GNU>,$<VERSION_LESS:$<CXX_COMPILER_VERSION>,9.0>>:stdc++fs>)